The present invention relates generally to antenna designs and manufacturing. More particularly, the present invention relates to a method of manufacturing antennas using micro-insert-molding techniques, and antennas manufactured using such techniques.
Antennas for portable wireless devices include both internal and external types. Portable wireless devices include cellular telephones, cordless telephones, and personal digital assistants (PDAs). Further, with the advent of wireless data communication standards such as Bluetooth and IEEE standard 802.11, portable wireless devices include any sort of portable data processing or communication device. In many of these portable wireless devices, antennas are mounted externally and include, for example, extendable whip antennas. In an increasing number of portable wireless designs, however, internal antennas are favored for their reduced size, cost and weight, as well as providing a more attractive appearance to the portable product since the entire antenna is hidden from external view.
There are various realizations of internal antennas for portable devices, but the cost and size of these approaches often limits the industrial design of the product or compromises total cost. Antennas can be fabricated using metal, fiberglass (FR4) printed circuit board (PCB) material, foam combined with flex circuits, and a multitude of other common variations.
Antennas radiate at frequencies which are dependant on their geometry, their height above the ground plane, and the dielectric constant of the materials that they are made of. Of these defining features, height above the ground plane has the greatest affect on frequency of operation. Height is also the most difficult physical feature to maintain at tight tolerances. Length and width, as well as other features on the aperture of the antenna are very reproducible. These dimensions are in the plane of the antenna and can be defined accurately using standard lithographic or stamping processes. But due to the three dimensional nature of the end product, the antenna""s height is far less controllable.
Current fabrication techniques to construct antennas typically stack various sub-components. The most common construction is illustrated in FIG. 1, which shows a prior art surface mount antenna assembly 100. FIG. 2 is a cross-sectional view of the antenna assembly 100 taken along line 1--1xe2x80x2. The antenna assembly 100 includes a sheet metal antenna 102 and a plastic support 104 mounted on a ground plane 106. Construction of the antenna assembly 100 requires bending the sheet metal 102 into the desired antenna shape, and draping the antenna sheet metal 102 over the plastic stand-off or support 104, as shown in FIGS. 1 and 2. This induces significant variability in the height of the antenna. Also, even if the antenna is fabricated perfectly, the final height realized in the customer""s product is susceptible to variation due to assembly tolerances. This is especially true for antennas that are not surface mountable using standard surface mount technology (SMT) processes. Antennas that have to be soldered on to a printed circuit board (PCB) by hand, or rely on spring contacts, can see height variations approaching 10%.
Manufacturers of wireless devices such as handsets, PDA""s and laptops are constantly pressured to reduce the size and cost of their products. Existing antenna solutions require significant space, add weight, increase cost, and most importantly, often compromise production yields. The frequency of operation and performance of an antenna is very dependant on the antenna""s physical dimensions, especially the height between the radiating element and the ground plane. Hence, one of the major cost drivers when fabricating high-volume antennas is reproducibility of the antennas themselves.
Accordingly, there is a need for an improved antenna and method for manufacturing antennas that meets these requirements.
By way of introduction only, the present invention may be applied in any of a variety of embodiments. In accordance with one embodiment, an antenna includes a molded plastic spacer and a metal insert. The plastic spacer is configured for mounting to a printed circuit board (PCB) to keep the metal insert a predetermined distance from a ground plane.
In a second embodiment, an antenna includes an injection molded plastic insert which has a body and a mounting portion extending from the body. The plastic insert is configured for surface mount engagement with a PCB to maintain the body a predetermined distance from a ground plane of the PCB. The antenna further includes a metal insert including a radiating portion molded with the body of the plastic insert and a ground lead and feed extending along the mounting portion of the plastic insert for electrical engagement with the PCB.
In another embodiment, an antenna tape and reel package includes plurality of antennas. Each antenna is formed by injection molding one metal insert of a tape of substantially identical metal inserts in a plastic insert. The plastic insert is sized to position the metal insert a predetermined distance from a ground plane when the antenna is assembled with a PCB. The antenna tape and reel package further includes indexing apparatus for moving the plurality of antennas through an automated printed circuit board assembly system.
In still another embodiment, an antenna manufacturing method includes positioning a metal insert in a mold cavity and filling the mold cavity with plastic to form a plastic spacer. The plastic spacer is shaped to position the metal insert a predetermined distance from a ground plane of a PCB when the plastic spacer is mounted to the PCB.
The foregoing summary has been provided only by way of introduction. Nothing in this section should be taken as a limitation on the following claims, which define the scope of the invention.